Exemplary embodiments of the invention relate generally to a system and method for improving the power handling capabilities of an electronic device, such as insulated gate bipolar transistor (IGBT) inverters. Moreover, such exemplary embodiments may relate to modeling, monitoring, and reducing the temperature of IGBT inverters.
Traction vehicles such as, for example, locomotives, employ electric traction motors for driving wheels of the vehicles. In some of these vehicles, the motors are alternating current (AC) motors whose speed and power are controlled by varying the frequency and the voltage of AC electric power supplied to the field windings of the motors. Commonly, the electric power is supplied at some point in the vehicle system as DC power and is thereafter converted to AC power of controlled frequency and voltage amplitude by a circuit such an inverter, which includes a set of switches such as IGBTs. In some systems, the electric power may be derived from a bank of electrical batteries coupled to a leg of the inverter.
In operation, IGBT inverters may experience an out-of-saturation operation, in which the IGBT inverter is in, or just turned to, an “on” state while an associated compliment module (for example, an IGBT, diode or bus bar) or the load have failed and represent a short circuit. Further, IGBT inverters may experience a low voltage power supply out of range condition.
Known methods of addressing out-of-saturation conditions include inserting a relatively large resistance in series with an external resistor Rg. In these methods, the rate of reduction of the current is very slow. Thus, if the device restricts the short circuit current to a first level, during the “soft switching off” provided by the added resistance, the first level may not decline to an acceptable level. The timing of the current reduction may also need to be controlled in a relatively precise manner do prevent damage to the IGBT device Improved systems and methods of detecting these conditions and responding to them are desirable.